The difference between ethical atheism and nihlism is that ethical atheists have more faith

[Question Mark]

I think it's definitely true a naturalist can value human life. But I don't think he can rational justify his properly basic beliefs of human value. I think this is why most societies resorted to belief in myth or supernatural.

It's very arguable that ancient leaders saw a distinct problem with everyone having a sense of "self", where accountability is only to those around them. People can be greedy, selfish bastards. Having a nice, unassailable authority figure to point to and say "I might not be able to stop you, but HE certainly can!" would likely explain early onsets of religion on the state level.

In the modern day though, I think we've learned to place our sense of morality upon the discovery that we evolved a sense of empathy, since it's counteractive to survival to foster a murderous culture.